Magnetic choking device.



H. H. & W. GIFFOHD.

MAGNETIC CHOKING DEVICE.

APPLICATION mw JUNE 10. me.

m u 7 z J P f 6/ M z w w. w C 2 G Y\ c 0 0 2a a d 7 d. /V/W/// Md 1., 1u a- J 32 W 6 7 .w w 7/// c 1 J j Attorneys ED STATES PATENT OFFICE.

HIRAM H. G'IFFORD AND WILLIAM GIFFORD, OF TRAVERSE CITY, MICHIGAN.

MAGNETIC CHOKING DEVICE.

Y '0 all whom 'it may concern Be it known that we, HIRAM H. Grrronn and'WIILIAM G rronn, citizens ofthe United States, residing at TraverseCity, in the county of Grand Traverse, State of Michigan, have inventeda new and useful MagneticGhokin Device, of which the followin 'is aspecication.

'- he present invention appertains to chok- -ing devices such as areused in electrical conductors, and aims to provide a novel and improvedyet-simple and inexpensive magnetic choking'device for use in electricservice and transmission lines in conjunction with ordinary lightningarr-esters for the protection of a transformer or other electricalequipment against damage by lightning.

It is the'object of'the invention to provide a magnetic choking devicewhich will arrest or retard "the instantaneous rush -or surge ofelectricalcurrent past the choking device to the electrical apparatus,as when the conductor is charged by a stroke of lightning or other' highfrequency electrical disturbance of similar nature, whereby "to protectthe electrical apparatus and to give the lightning arr-ester suilicientopportunity to act before the high frequency current can pass thechoking device.

With the foregoing and other objects in view which will appear as thedescription proceeds, the invention resides in the combination andarrangement of parts and in the details of construction hereinafterdescribed and claimed, it being understood that changes in the preciseembodiment of the invention herein disclosed can be made within thescopeof what is claimed without departing from the spirit of the invention.

The invention is illustrated inthe'accompanying drawing, wherein Figure'1 is a longitudinal section of one form of the choking device, portionsbeing shown in elevation.

Fig.2 is a similar view of another form.

Fig. 3 is an elevation of a third form of the invention, portions beingbroken away and shown in section.

Fig. t is a view similar to Fig. 3 of another variation.

Specification of Letters Patent.

Patented Julyfi, 191-7.

Application filed June 10, 1916. Serial No. 102,989.

longitudinal bore or recess 2 extending from one end -'to a pointadjacent the other end, there being a reduced aperture 3 extending fromthe last mentioned end of the body to the bore Threadedly or otherwiseengaged within the aperture dis a bushin 4 of insulating material, whichis provi ed with a convexed hood 5 for shedding rain and moisture to thesides 'of the body, the present device being adapted especially for usein a vertical position with "the bushing 4 at the upper end of the body.Another bushing or plug=6 of insulating material is thre a dedl-y or=othcr-wise engaged within the lower end otthe bore 2, and has'anenlargement 7 resting against the lower end ofthe body 1. As aconvenient means *for sup porting the body 1 one side thereof can beformed or provided with an outstanding screw 8 to be threaded into thecross arm ofthe pole which supports the conductors, although the bodyl'can be supported in any suitable manner. The bushings 4 and 6 areapertured for-the passage of the conductor 9 'therethrough, and saidconductor has a coil or helix 10 within the bore 2 between the bushingor plug 6 and the shouldered end of the bore 2, said conductor beinginsulated to insulate it from the 'body 1.

In practice, the choking device is interposed in the conductor betweenthe lightning arrester and electrical equipment (not shown) to beprotected, and should the con ductor 9 be struck by lightning orotherwise subjected to a high frequency electrical disturbance ofsimilar nature, the choking device will retard or check the flow ofcurrent to'the electrical apparatus, thus protecting it from injury inconnection with the lightning arr-ester. The lightning arrester is thusgiven an opportunity to act in order to prevent the abnormally highvoltage-current from passing to the electrical equipment. An ordinarycurrent will flow along the conductor past the body 1 without difiicultyw'herethenumber of turns of the helix are of proper ratio to theamountof current flowing through the conductor, but with lightning orsimilar electrical disturbance, the conditions are reversed. Lightningor equivalent high frequency electrical current will leave a completemetallic path of low ohmic resistance and jump an air gap that a normalline current would not, rather than pass the mag netic choking device.This is due to the high self induction set up in the magnetic chokedevice by currents of a highly oscillatory character, such as producedby lightning. The conductor in extending past the iron or steel body 1provides the choking effect due to the fact that a high frequencycurrent will set up magnetic fields in the body 1 which resist the flowof the high frequency current.

The device can be used wherever necessary, and while applicable toindoor installations, is especially adapted for out door service, toprotect out door transformer installations, meters, etc. The surface ofthe body 1 and insulating bushings can be coated by enamel or othermaterial whereby to protectthe device from the elements. The device canbe constructed in different sizes and proportions for currents ofdifferent voltage, and is adapted to supersede the more expensive andless efiicient choke coils now in use for the service that the presentchoke device is designed. The present device is thoroughly eflicaciousin use, is easily installed, is non-destructible, and is cheaper andsuperior in many respects over choke coils which are commonly used. Thebody 1 is of such formation and is associated with the conductor in sucha way that in the presence of a high frequency current, the magneticfield is set up in the body proportionateto the flow of current, andthis consumes a sufficient period of time during which the .potentialbuilds up, between the magnetic choke device and conductor to a pointsufficiently high, to cause the lightning arrester to discharge andcarry the current to ground. In so doing, the apparatus protected isrelieved from the great strain it would otherwise be subjected to, andthe danger of a break down is greatly lemened. The body 1 also protectsthe helix 10. The interior as well as the exterior of the device can becoated by enamel, or the like, to insulate and render the device weatherproof.

The device shown in Fig. 2 is of slightly different formation than thatshown in Fig. 1,. This second form of the device is of the hour glasstype, the iron or steel body 1 having the hour glass bore 2* which is ofa constricted diameter between its ends and which increases in diametertoward the ends of the body 1. This device, the same as that shown inFig. 1, is adapted for use in a vertical position, although it-can beused in a horizontal or other position. -A bushing 4 of insulatingmaterial is threaded or otherwise engaged within'the upper end of thebody 1 and is provided with a convexed portion. 5 for shedding rain, andthe like. A bushing or plug 6 of insulating material is threadedly orotherwise engaged within the lower end of the body 1 and has an enlargedportion 7 bearing against the lower end of the body. ,The bushings 4 and.1

(1 are aperturcd for the passage of the conductor 9, which is providedwith a hour glass type of coil 10fitting snugly within the bore 2. Theexterior of the body 1 is also preferably shaped as seen in Fig. 2, inpreference to the shape of the body 1. The body and bushings can beenameled exteriorly and interiorly to protect them from the elements,and due to the use of the hour glass coil 10, the device is particularlyefficient for its intended purpose.

The device shown in Fig. 3 has an external instead of an internal coilas used in the devices shown in Figs. 1 and 2.

The device in Fig. 3 has a body 1" of ovoid form, and provided with a10m 'tudinal bore 2 extending therethroug and through which a bushing 4"of insulating material extends, said bushin being tubular for thereception of the con uctor 9". The body 1 is provided with a helicalgroove 11 in its periphery or circumference,.the

axis of said groove being coincident with the axis of the body, and thebody has radial bores 12 extendin from the ends of the groove 11 to theushing 4" through which the conductor 9" extends, and said conductor hasa coil or helix 10 seated within the groove 11". The groove 11" ispreferably filled with insulating cement or equivalent material 13, andthe surface of the body and bushing are preferably enameled or similarlyfinished.

Figs. 4 and 5 illustrate a squirrel cage type of choking device,embodying the body 1 of iron or steel, and provided with a lon gitudinalbore 2 through which the insulated bushings 4 extends, the conductor 9extending straight through the bushings 4. The body 1 is provided uponits exterior with longitudinal grooves 11 and with annular grooves 11 atthe ends of the grooves 11, and .longitudinal strips 10 are seatedwithin thegrooves 11 and have their ends secured to rings 10 lyingwithin the grooves 11, to provide the squirrel cage. The grooves 11''and 11 are filled with insulating cement 13 and the device is coatedwith enamel or equivalent material to protect the same from theelements. It has been found that a high frequency current passes withgreat difficulty through this type of magnetic choking device.

The enamel and cement used provide for the insulation of the device aswell as protecting it-from the elements.

Having thus described the invention, what is claimed as new is:

1. A ma etic choking device embodying a thick-wal ed tubular body ofmagnetic material, insulation therein projecting from its ends, aconductor extending into and out of said body through said projectingortions of the insulator and provided therebetween with a coilinclosedby the body, to provide Choking effect to a high frequency current.

2. A magnetic choking device embodying a thick-wa1led tubular body ofmagnetic material having a helical groove in its periphery, insulatingmaterial Within said body projecting from the ends thereof, and a eonduetor extending into and out of the ends of the body through theprojecting portions 10 of the insulating material and having a coilthercbetweeu seated in said groove and inelosed by the body.

In testimony that we claim the foregoing as our own, we have heretoallixed our signatures in the presence of two Witnesses.

HIE-AM H. GIFFORD. \VILLIAM GIFFORD.

\Vitnesses MINNIE (ls'iimi nicn ALMA D. THOMPSON.

Ccpies of this patent may be obtained for five cents each, by addressingthe "Commissioner of Patents, Washington, I). C.

